Mercury MerCruiser MCM 454 Mag MPI Service Manual page 574

SERVICE MANUAL NUMBER 23
Lack of Power, Sluggish or Spongy Symptom (Continued)
Index
90-861326--1 MARCH 1999
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1. Check for intermittent opens or short
to grounds in the ECT sensor, MAP
sensor and TP sensor circuits. Also
check or throttle linkage sticking,
binding or worn.
12
2. An intermittent failure may not store
a DTC.
3. If a problem is found, repair as
necessary.
Was a problem found?
1. Check ECM grounds for being
clean, tight and in their proper
locations.
13
2. If a problem is found, repair as
necessary.
Was a problem found?
1. Check for engine going into rpm
reduction mode.
14
2. If a problem is found, repair as
necessary.
Was a problem found?
1. Check diagnostic test CKT 451 for
being shorted to ground. This will
cause the rpm to be lowered.
15
2. If a problem is found, repair as
necessary.
Was a problem found?
1. Check or proper alternator voltage
output.
2. The voltage should be between
16 specified values.
3. If a problem is found, repair as
necessary.
Was a problem found?
1. Check for the following Engine
Mechanical problems:
Low compression.
Leaking cylinder head gaskets.
Worn or incorrect camshaft.
17 Proper valve timing/valve train prob-
lem.
Restricted exhaust system.
2. If a problem is found, repair as
necessary.
Was a problem found?
FUEL INJECTION SYSTEM TROUBLESHOOTING
Go to OBD
System
-
Check
Go to OBD
System
-
Check
Not
Applicable
to
MerCruiser
-
EFI or MPI
Go to OBD
System
-
Check
Go to OBD
11-16
System
Volts
Check
Go to OBD
System
-
Check
Go to Step 13
Go to Step 14
Go to Step 15
Go to Step 16
Go to Step 17
Go to Step 18
Page 5D-15